This is not a conceptual project, it will be built it in a backyard, so the plans (you create) will need to be very clear for a contractor or handyman to build them.
I'm thinking the interior of the treehouse will be between anywhere from 10x10 to 10x15 (probably at the biggest). I have a list of items I want, and some pictures of ideas of different features I want it to have, and of coarse there are items to consider that are very important. We don't have big trees, so essentially it is a playhouse on stilts (hence the "free-standing" part).
Efficiency, yard location, functionality, safety, super fun features, and durability are key. This is where your good planning comes into play. The heat here is horrific, it wears and destroys materials very fast. I want something to look great and last for 15+ years.
I want this to be a dream come true and the funnest treehouse ever! As far as the chicken coop, our current chicken coop is old, and I think it would be neat to have it match the finish of the treehouse, but have it be beautiful, functional, and have some neat features for the chickens (and on wheels to easily move it in the yard).
3d rendering is a must, I want to see how it will look, but your plans are a must to have a step by step, list of materials, and instructions for the handyman to build it.